Material handling apparatus such as mailing machines commonly employ rollers and/or belts for transporting and separating sheet material. In the context used herein, “sheet material” is used generically to describe any substantially flat, two-dimensional media such as mailpieces, sheets of paper, postcards, laminate, woven material/fabric etc. Oftentimes, a combination of belts and rollers are employed, i.e., one set of rollers opposing a set of belts, to separate individual sheets from a stack of sheet material.
A common singulating apparatus, used in a variety of mailing machines/meters, employs a set of horizontal conveyor belts (typically three) moving in one direction along a transport deck and a pair of rollers disposed above and rotating in a direction opposing the conveyor belts. The belts typically transport a stack of mailpieces toward a V-shaped ingestion area or throat disposed between the rollers and the belts. The V-shaped ingestion area converges such that the rollers and belts define a singulation interface which is initially spring-biased to a closed position, but may open in response to loads imposed by mailpieces entering the ingestion area.
More specifically as mailpieces approach the V-shaped ingestion area, the opposing motion of the upper rollers causes the mailpieces to shingle such that the lowermost mailpiece of the stack enters the singulation interface. Preferably, the ingestion angle, i.e., the apex angle of the V, should be shallow to ensure that mailpieces are separated in the throat before reaching the interface. As the conveyor belts move mailpieces against the upper rollers, the interface opens due to the normal forces acting on the rollers. Furthermore, the friction force developed between the mailpiece and the conveyor belt is designed to exceed the retarding force developed between the mailpiece and the upper rollers such that the mailpiece passes through the interface and is “singulated” from the stack.
A variety of factors associated with the geometry and arrangement of the opposing rollers/belts can be difficult to control and/or to optimize the effectiveness/of the singulating apparatus. Of the various difficulties which can arise, a principal concern relates to leading edge damage as a mailpiece enters the singulating interface. More specifically, as the leading edge of a mailpiece contacts the singulating upper rollers, the leading edge can peel upwardly and fold back upon itself as a consequence of the opposing motion of the rollers. In addition to the leading edge damage, the build-up of thickness can jam and stall the operation of the singulating apparatus.
Moreover, the geometry of, and friction forces developed in connection with, the ingestion assembly, i.e., the combination of the singulating guide and rollers, can impact mailpiece shingling/separation and the effectiveness of the singulating roller(s). More specifically, difficulties are often encountered when processing/singulating: (i) mailpieces spanning a wide range of thicknesses, (ii) a combination of thick and thin mailpieces and/or (iii) mailpieces having a variety of surface finishes i.e., glossy, satin or flat surface finishes. Regarding the former, the geometry of the ingestion area, i.e., principally the ingestion angle, can cause a collection of thin mailpieces, or a single thick mailpiece, to change the effectiveness of the singulating roller. More specifically, a build-up of mailpieces upstream of the singulating roller can lift the ingestion assembly so as to cause multiple mailpieces to pass under the roller without being singulated. Additionally, the thickness of mailpieces contacting the singulating roller can ameliorate or exacerbate the effectiveness of the roller.
Regarding the latter, the surface finish determines the friction coefficient and, consequently, friction forces developed between various elements of the singulating apparatus. More specifically, the surface finish impacts the friction forces developed between (i) individual mailpieces, (ii) mailpieces and the upper ingestion assembly and, (iii) the lowermost mailpiece of the stack and the lower conveyor belts. Generally, the friction forces developed in one of these areas, must be higher or lower than the forces developed in another area. For example, the friction forces developed between the lower conveyor belt and the lowermost mailpiece must be higher than the forces in any other area for successful mailpiece singulation. Additionally, the friction forces developed between the upper ingestion assembly and the contacting mailpieces must be higher than the friction forces generated between individual mailpieces for successful mailpiece shingling. It will be appreciated, therefore, that the surface finish of mailpieces further complicates the shingling/singulation of mailpieces in a singulation apparatus.
A need, therefore, exists for an ingestion assembly for a singulating apparatus which accommodates both thin and thick mailpieces, is reliable, low-cost and mitigates damage to the leading edge portion of sheet material without impacting the efficacy and/or efficiency of a singulation apparatus.